Telephone system



June 14, 1932. v, CURLEY 1,863,086

Filed Sep't.- 1, 193.1

INVENTOI? T. V. CURL E! A T TORNE Y Patented June 14, 1932 PATENT FFICE THOMAS V. CURLEY, 0F BROOKLYN, NEW YORK, ASSIGN'OR TO BELL TELEPHONE LABO- RATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NE'W YORK TELEPHONE SYSTEM Application filed September 1, 1931. Serial No. 560,550.

This invention relates to telephone systems and particularly to signaling systems.

The objects of this invention are to simplify signaling over trunk circuits and to econo mize in the use of power equipment for alternating current signals in telephone systems by employing direct current sources for signalin over trunks.

Heretofore; direct current has been used for signaling over trunks to operate signals or light lamps at the distant end of the trunks. In systems of this kind, when an operator at the distant end of the trunk answers a signal by connecting the trunk to a subscribers line, the fact that this direct current signal is received and that the operator has established the connection causes an alternating current ringing signal to be produced to call the sub scriber on the connected line. 133 It is a feature of this invention to provide an arrangement for signaling over trunks to recall a subscriber on a connected line by direct current means. A direct current sig nal produced at an operators position is passed by a repeating coil at the toll oflice and caused to open the connection between the tip and the ring conductors of the trunk. At the call originating ofiicc this signal is passed by a repeating coil and translated into an alternating current signal for recalling the calling subscriber.

It is another feature of this invention to employ this si nal in systems where supervisory signals are also transmitted over the trunk by the usual high-low marginal and reversed battery supervisory systems.

This invention may be applied to recording completing trunk systems in which a connection has been established over the trunk from a local office to an operator at a toll oflice and in which the usual supervisory signaling arran genient is employed.

The usual supervisory signaling over the trunk is accomplished from the local oflice by reversing the tip and ring conductors to a local battery and ground connection for the trunk and thereby cause the operation of a relay having a high and lower resistance winding bridged across tip and ring conduc- 39 tors at the toll office. This relay in operating lights the usual line lamp. The toll operator then inserts the plug of a toll cord into the jack of the trunk, and thereby causes the line lamp to be extinguished and also causes the high resistance winding of this relay to be short-circuited. This in turn causes the usual supervisory relay at the local office to operate to place the release of the connection from the subscriber to the toll operator under control of this operators cord circuit. The invention is applied to this system by providing a special relay bridged across the conductors at the local office in series with the supervisory relay. This relay operates simultaneously with the operation of the supervisory relay. At the toll oiiice the arrangement may be such that when the toll operator desires to recall the calling subscriber she will apply a direct current signal to the tip conductor on the toll office side of the usual repeating coil inserted at this end or" the trunk and thus cause a relay at this end of the trunk to open the connection between the tin and ring conductors of the trunk connected through the outgoing side of the repeating coil. This in turn causes the supervisory relay and the special relay at the local oflice to release. The circuit arrangements at the local ofiice are now such that a ringing relay is thereby operated to apply an alternating current signal to the calling subscribers line to recall this subscriber.

This invention has been illustrated in the accompanying drawing in connection with a call recording and completing trunk extending between a local office and a toll oflice.

Referring to the drawing the line of a calling subscriber at A has been shown connected through switches LF and S, shown in diagrammatic form and representing standard line finder and selector switches in an automatic telephone exchange, or local office B, to a trunk line RC terminating at a toll ofiice C in a jack J. From jack J the connection may be extended through a standard toll operators cord circuit TO to a called subscribers line at D. The cord circuit and the called subscribers line have also been shown in diagrammatic form.

To show the application of the applicants invention to a system of this kind, a call will be described from the calling subscriber at A to the called subscriber at B and the recalling of the calling subscriber by the toll operator at C. If the calling subscriber at A in any manner well known in the art causes a connection to be established to the trunk RC through the line finder LF and the selector S,

a circuit is completed from battery, lower repeating coil 2 and upper winding of-relay 1 to ground. This causes the operation of'relay 1, which in turn closes an obvious circuit for the operation of relay 4 and this latter relay in turn closes an obvious circuit for the operation of relay 5. Relay .5 in operating closes a signaling path fromrthe tone source T to the ring conductor back to the calling subscribers set to notify him that the toll'operator is being called.

Relays 4 and 5 in operating close a connection from battery and ground over the trunk 7 RC to the toll oflice C as follows: From battery through the lower windings of relays 6 and 7 in series, lower inner armature and front contact of relay 5, upper inner armature and front contact of relay 4, upper right hand windin of re eatin coil 2 tip con- 19 P g a ductor of trunk RC, upper left hand winding if repeating C01l,8, upper armature and back contact of relay 9, upper and lower WI'ILClIDgS of relay 10 in series aiding, lower armature and back contact of relay 9, lower left hand winding of repeating coil 8, ring conductor of trunk RC, lower right hand winding of repeating coil 2, lower inner armature and front contact of relay 4, upper inner armature and front contact of relay 5, and upper windings of-rela-ys 7 and 6 in series to ground. The operation of relays 4 and 5 also completes another circuit for the operation of relay 11 from battery, winding ofth-is relay, lower outer armatures and front contacts of relays5and4toground. Relayll closes at its upper armature and front contact. a connection to ground for the sleeve circuit through the selector S to maintain the connection in the usual manner through the selector S and the line finder LF for the calling subscribers line. The connection established over the trunk RC causes the operation of relay 6 at the local ofiice B and relay 10 at the toll office CL Relay 6 opens at its armature and back contact the circuit established by relay 11 for relay 3. The purpose of the operation of relays 11 and 6 will become apparent hereinafter. Relay 10 in operating closes a circuit forthe operation of relay 12from battery, winding of this relay, lower inner armature and back contact of relay 13, a-rmature and front contact of relay 10 to ground. Relay 12 in operating closes an obvious circuit for the lighting of lamp 14 to indicate to the toll operator that a call is waiting on this trunk.

When the operator answers this call by ination of relay 17. Relay 17 closes at its lower armature and front contact a. shunt circuit for the lower high resistance winding of relay 10 and at its upper armature and front contact establishes a connection between the left hand windings of repeating coil 8 through condenser 20 to establish a talking path through the repeating coil. The reducing of the resistance trunk RC causes the marginal relay 7'to operate. This relay in operating closes an obvious circuit for the operation of relay 22 and this latter relay in operating closes at its upper armature and front contact a connection between a tip and ring conductor of the truck through the right hand windings of repeating coil 2 and condenser 23 to establish the talking connections through this repeating coil. Relay .22 in op erating opens the hereinbefore mentioned. signaling path from the tone source T established on the operation of relay 5 to the calling subscribers telephone. This indicates to the calling subscriber that the toll operator has answered. The calling subscriber may now converse with the toll operator and inform her of theconnection desired. The toll operator may then complete the connection to the desired subscribers line at D whereupon conversation betweenthe two subscribers may take place.

In the, foregoing description it has been shown how supervisory signals may be transmitted over the trunk TC from the local oflice B to the toll office C and from the toll ofiice to the local office. A description will now be made showing how the operator may recall the calling subscriber without interfering with supervisory signals of the above description. In case the toll operator desires to recall the calling subscriber she completes a circuit to battery, not shown, in the cord over the tip conductor to cause the operation of relay 9. Relay 9 in operating opens the connection over the tip and ring conductors of the trunk RC and thereby causes the release of relays 6 and 7. Relay 6 in releasing rent from the source 28 over the tip and ring conductors to the calling subscribers line to recall this subscriber. It will be noted that relay 22 will release on the release of relay 7, but being slow in releasing, it will prevent the tone circuit from being completed at its lower armature and back contact before the operation of relay 3 so that no tone will be transmitted to the calling subscribers line during. recall signaling. When relay 3 operates, relays 1 and 4 may release, but relay 11 is maintained operated by the connection to ground for this relay is closed by the operation of relay 3 at its lower outer armature and front contact. The purpose of the slow releasing feature of relay 22 is also to maintain relay 11 operated after relay 4 is released and until relay 3 is operated, thus serving to maintain relay 11 operated during this recall signaling period. When the operator ceases to signal the calling subscriber, relay 9 is released and the circuit is again completedover the trunk for the reoperation of relays 6 and 7. Relay 6 in operating opens the circuit for relay 3 to discontinue the re call signaling of the calling subscriber. It should be noted that when relay 3 releases,

the circuit for relays 1 and 4 are reestablished.

The operation of relay 7 causes the operation of relay 22 to maintain relay 11 operated after relay 3 is released and until relay 4 is reoperated. Relays 3 and 11 have been shown slow to release in order to further insure the proper sequence of operations as described above. Thus it will be seen that in recalling the calling subscriber, the consequent circuit changes at the local oflice do not disturb the maintaining of the connection from the calling subscriber through the trunk as maintained by the operation of relay 11 over the upper armature and front contact.

While the invention has been illustrated and described in connection with but one disclosure, it should be understood that it could readily be applied to other systems without departing from the spirit thereof and that the present disclosure should only be taken as illustrative of one application of the invention.

What is claimed is:

1. In a telephone system, a local oflice, a toll oflice, a subscribers line terminating in said local oflice, a trunk between said oilices, means for connecting the subscribers line to the trunk at said local office, means responsive to said connection for signaling the toll oflice and means for signaling the calling subscriber from the toll office by opening the connection between the tip and ring conductors of the trunk without releasing the connection between the calling subscriber and the trunk.

2. In a telephone system, a trunk, a repeating coil inserted in said trunk near each end thereof, means responsive to the application of a direct current signal to one conductor at one end of the trunk for opening the connection over the tip and ring conductors of the trunk between the repeating coils, a source of ringing current and means responsive to said opening for connecting said source of ringing current to the trunk at the opposite end thereof.

3. In a telephone system, a local ofiice, a toll ofiice, a trunk between said ofiices, a repeating coil inserted in said trunk near each end thereof, means for signaling from the local ofiice to the toll ofiice including the reversal of current over the trunk between the repeating coils, means for signaling from the toll oflice to the local office including the decreasing of the resistance of the trunk between the repeating coils and means for signaling from the toll ofiice to the local ofiice over said trunk past the repeating coils including the opening of the connection over the tip and ring conductors of the trunk between the repeating coils.

4. In a telephone system, a subscribers line, an operators position, a trunk terminating at said position, a cord at said position, means for establishing a connection from the subscribers line to said trunk, a signal at the terminating end of the trunk, means responsive to said connection for actuating said signal, means responsive to the connection of the cord to the terminating end of the trunk for disabling said signal and for transferring control over said first mentioned connecting means to said cord to maintain it established, means responsive to the replacing of the receiver on the switchhook by the subscriber of said line for reoperating said signal, means for opening the connection between the tip and ring conductors of the trunk. and means responsive to said opening for signaling the subscriber on said line.

5. In a telephone system, a subscribers line, an operators position, a trunk terminating at said position, a cord at said position, means for establishing a connection from the subscribers line to said trunk, a signal at the terminating end of the trunk, means responsive to said connection for actuating said signal, means responsive to the connection of the cord to the terminating end of the trunk for disabling said signal and for transferring control over said first mentioned connecting means to said cord to maintain it established, means responsive to the replacing of the receiver on the switchhook by the subscriber of said line for reoperating said signal, means for opening the connection between the tip and ring conductors of the trunk, and means responsive to said opening for transmitting an alternating current signal over the subscribers line.

6. In a telephone system, a trunk, means for signaling from one end of the trunk to the other including a direct current signal applied to the tip and ring conductor of said trunk, means for signaling from the opposite I ing coil at the end ofthe trunk including the decreasing of the resistance of the tip and ring conductors of the trunk, and means for signaling from said opposite end of the trunk including the opening of the connection between the tip and ring conductors of said trunk.

7 In a telephone system, a local oflice, a toll office, a trunk between said oflices, a repeating coil inserted in said trunk near each end thereof, means for signaling from the local office to the toll office past the repeating coil 'at'this end of the trunk including the application 01": a direct current signal over the tip and ring conductors of said trunk, means for thereafter signaling from thetollofiice to the local oliiceinc'luding' the decreasing of the resistance of the tip and ring conductors of said. trunk between said repeating coils and means for thereafter signaling from the toll office to the-"local oliice past therepeating coils including the opening of the connection between'the tip and ring conductor between therepeating coils.

8. In a telephone system, a local oiiic'e, a

toll ottice, a trunk between said ofiices, a repeating coil inserted in said trunk near each end thereof, a subscribers' line at the local oflice, means for establishing a connection between said subscribers line and said trunk at said local office, means responsive to said connection for signaling over the trunk, a signal at the toll oflice, means responsive at the toll oflice to said signaling for actuating the signal at the toll ofiice,.an operators cord at said toll ofiice, means for connecting said cord to the trunk, means responsive to' said last mentioned connection for disabling the signal at the toll office and for signaling the local ofliceover said trunk, means responsive to said signaling from thetoll office for holding the connection between the calling subscribers line-and the trunk under control of the cord, means for signaling past therepeattoll oflice over the trunk and past the repeating coil at the local oflice. including the opening of the connection between thetip and ring conductors of the trunk between therepeating coils, and means responsive to the last mentioned signaling for transmitting-an alternating current signal over the snbscribers line to call the subscriber. v

9. In a telephone system, a trunk, a repeating coil inserted in said trunk near each end thereof, means-responsive to the application of a direct current signal at one end of said trunk for opening the connection between 7 10. 111 a telephone system, a local office, a toll oflice, a trunk between said oiiices, a repeating coilinserted in said trunk near each end thereof, means for signaling from the local oflice'to the toll office including the"- means responsive tothe operation ofsaid' relay at the toll oiiice for actuating said signal, means at said toll office for closing a connection between said tip and 'ring conductors past a portion of the winding of said relay at said toll oliice, means responsive to the closing of said last mentioned connection for operating the other relay at the local office for signaling at said local oflice, means for opening the connection between the tip and ring conductorsbetween said repeating coils at the toll ofiice to cause the release of said relays at the local ofiice, and means responsive to the release of the first mentioned relay at the local of'ice for signaling beyond the repeating coil at said local oflice towards the" end of said trunk; 7

11. In a telephone system, a local oflice, a toll oifice, a subscribers line terminating at said local office, a trunk between said ofiices,

au' tomat-ic means for connecting the subscribers line to the trunk at said local oilice, means responsive to said connection for closing the tip and ring conductors of said trunk, two relays atthe local oflice, a relay at the toll office, means responsive to the closing of the tip and ring conductors for operating one of the relays at the local office and the relay at the toll oifice, means responsive to the operationof the relay at the toll otfice for signaling the toll oflice, means at said toll ofiice for closing a connection between the tip and ring conductors of the trunk betweenthe repeating coils past a portion of the winding of said relay at thetollofiice, means responsive to said last mentioned connection for operating the other relay at said local'oflice, means responsive to the operation of said other relay for maintaining the connection between a calling subscriber and the trunk circuit at said local oftice and for signaling the subscriber, means at said toll off ce for opening the connection between the tip and ring conductors to release said two relays at the local office, and

means responsive to the release of said first M mentioned relay at the local office for signaling the subscriber.

In witness-whereof, I hereunto subscribe my name this 31 day of August, 1931.

THOMAS, V. CURLEY.

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